The invention relates to an apparatus and concomitant method for controlling and monitoring a decoder system. More specifically, the present invention incorporates an interface structure having a status interface line and a plurality of data interface lines and concomitant communication protocol to allow a video decoder to communicate with an audio decoder.
The proliferation of digital video/audio information presents a challenge for systems that are tasked with receiving and decoding such complex information. Namely, digital information, e.g., a movie or a xe2x80x9clivexe2x80x9d broadcast from a digital studio or from a storage device, is often converted into compressed bitstreams before being transmitted or stored. The compressed bitstreams contain various data elements that include video, audio, timing, program specific information and control data which are packaged into various xe2x80x9cpacketsxe2x80x9d. A packet is a group of binary digits that include various data elements that are switched and transmitted as a composite whole.
In turn, a decoding system must receive and decode the packets properly to extract the digital video/audio information. The data elements and other information are arranged in accordance with various specific formats, e.g., ISO/IEC international Standards 11172-* (Moving Picture Experts Group (MPEG-1)), 13818-* (MPEG-2), MPEG-4, American Television Standards Committee (ATSC) standards and Digital Video Broadcasting (DVB) specification prETS 300-468 are just several examples.
To illustrate, in general, MPEG defines a packet as consisting of a header followed by a number of contiguous bytes from an xe2x80x9celementary data streamxe2x80x9d. An elementary stream is simply a generic term for one of the coded video, coded audio or other coded bitstreams. More specifically, an MPEG-2 xe2x80x9ctransport streamxe2x80x9d packet comprises a header, which may be four (4) or more bytes long with a payload having a maximum length of 184 bytes. Transport stream packets are part of one or more programs that are assembled into a transport stream. The transport stream is then transmitted over a channel with a particular transfer rate.
As the transmission bandwidth increases in response to greater demand, it becomes increasingly more difficult to decode such an enormous amount of transmitted information, especially in real-time by a single decoder. As such, it is desirable that the decoding function be allocated such that two or more decoders can be employed to perform the decoding function, e.g., a video decoder to handle image information and an audio decoder to handle audio information. However, since the various components of the digital video/audio information, e.g., a video sequence and its associated audio frames, are closely related, the decoders must carefully coordinate their decoding functions to properly address numerous decoding and presentation issues, e.g., timing issues, lost information, servicing user selections, and the like. In fact, as the complexity of the digital video/audio information increases, the decoding system may employ a separate controller or a host to monitor the functions performed by the decoders, e.g., to arbitrate conflicts between the decoders.
Therefore, a need exists in the art for a method and apparatus for effecting communication between components within a decoding system. Specifically, a need exists for an interface and concomitant communication protocol to allow a video decoder to communicate with an audio decoder.
The present invention is a method and apparatus for using an interface structure having a status interface line and a plurality of data interface lines and concomitant communication protocol to allow a video decoder to communicate with an audio decoder. More specifically, the present interface structure allows multiple data streams to be passed between the two decoders by using control data or meta-data on the status interface line to inform the decoders as to which data interface lines are currently carrying relevant data that the receiving decoder should service.
The novel interface structure allows a communication protocol to effect communication of timing information and audio data transmission without having to add extra control data onto the data streams or to adhere to a strict time schedule as to which data interface line is actually carrying relevant data.